Six questions answered on Centrica's share price fall after suggestions British Gas could be broken-up

Why is Ed Davey investigating British Gas’s profit margins?

Ed Davey suggested British Gas had charged one of the highest prices to domestic customers in the last three years. Photograph: Getty Images.

British Gas owner, Centrica, suffered a fall in share price today after the UK energy secretary investigated its profit margins and suggested the company may have to be broken up. We answer five questions on the potential break-up of British Gas.

By how much has Centrica’s share price fallen?

The share price fell by 3 per cent today after energy minister Ed Davey questioned the company’s dominance in the market. British Gas currently has 41 per cent of the domestic gas supply market in the UK, the largest share of any of the so-called "big six".

Why is Ed Davey investigating British Gas’s profit margins?

Davey said in a letter that profit margins made by the "big six" energy suppliers when supplying gas were actually higher than previously thought. In particular, he highlighted the high profit margin of British Gas and its large market share. He added that British Gas had charged one of the highest prices to domestic customers in the last three years.

He estimated that if gas margins were similar to electricity households would save on average up to £40 a year. Davey also provided information that showed Centrica saw profit margins of 11.2 per cent for its gas business in 2012. He suggested a market investigation.

Why has Davey said British Gas may have to be broken-up?

If an investigation found evidence of a monopoly this could result in the company being broken-up. As well as asking the competition authorities to investigate the profit margins as part of an ongoing review, he has written to energy regulator Ofgem and the Competition and Markets Authority asking them to consider all possible avenues "including a break-up of any companies found to have monopoly power to the detriment of the consumer".

What else has Davey said?

Mr Davey told the BBC: "This is a significant issue for consumers out there who are struggling with their energy bills."

In his letter he says: "Analysis of the profit margins of the energy companies shows that the average profit margin for gas is around three times that of electricity.

"There is also evidence that British Gas, the company with the largest share of the gas domestic supply market, has tended to charge one of the highest prices over the past three years, and has been on average the most profitable."

What has British Gas said about Davey’s comments?

In its statement, British Gas said: "We welcome this and have complied with all the requests for data which we have received.

"The data referred to in the Secretary of State's letter has already been fully disclosed and in the public domain for a number of weeks."

What have the independent experts said?

Some have queried why this publicly available information hasn’t been investigated by Ofgem already.

However, Richard Lloyd, the executive director of the consumer rights group Which?, told the BBC the intervention was hugely significant and suggested Davey agreed with Which? that the structure of the biggest energy companies is partly to blame for the price hikes.

"It will now put huge pressure on the regulators, in a matter of weeks, to announce that they're taking the first steps towards potentially breaking up the very biggest of the big energy companies," he added.